1. Field of the Invention
The present invention relates to an actuator capable of rotational driving with a multiple-degree freedom.
2. Description of the Related Art
Conventionally, as a multiple-degree-freedom rotational driving mechanism employed for visual line change control of a monitor camera or the like, a spherical actuator and the like are proposed. According to one spherical actuator (JP-A 6-284673 (KOKAI)), motors similar to so-called brushless DC servo motors are combined to enable rotational driving with a multiple-degree freedom. According to another a spherical actuator (JP-A 2003-324936 (KOKAI)), a permanent magnet is arranged on a cap-like rotor and multiple-degree-freedom driving is implemented by employing an electromagnetic motor.
These conventional structures are not necessarily satisfactory because they have the following problems. For example, in rotational driving about the central axis of the rotor, positioning is effected intermittently at every 90°. Upon performing rotational driving about an axis perpendicular to the central axis of the rotor, rotational driving about the central axis of the rotor is difficult. Particularly, concerning rotor rotation, it is difficult to position the rotor accurately at an arbitrary position.